摘要:

AbstractSimple indices of the zonal and meridional surface circulation have been obtained for the months of the winter half year. The strength of the zonal circulation appears to be little related to the poleward flux of heat in this period. An index of the meridional circulation, measuring the strength of the main northerly and southerly currents, is much more closely related to the seasonal variation of heat flux and better represents the few year‐to‐year differences available. This result may be helpful in interpreting the secular changes in the zonal circulat

ISSN:0035-9009    

DOI:10.1002/qj.49710243403

出版商:John Wiley&Sons, Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractThe annual production of nitric oxide by lightning discharges is estimated to be 1.8 × 1035molecules, within rather large limits of uncertainty. Implications for the global budget of odd nitrogen species are cursorily examined. More data are needed to decide whether or not lightning‐produced nitrogen oxides are transported in significant quantities to the stratosphere.Closer studies of the budget of nitrate in rainwater, and of air trajectories in large cumulonimbus storms, are also indicat

ISSN:0035-9009    

DOI:10.1002/qj.49710243404

出版商:John Wiley&Sons, Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractThe structure and behaviour of planetary‐scale temperature waves in the stratosphere are described by the use of observations from the Selective Chopper Radiometer on the Nimbus 5 satellite during the two years from January 1973 to December 1974.From a latitude‐height diagram of monthly root‐mean‐square wave amplitudes, it is found that the planetary wave of wavenumber one is predominant in the upper stratosphere at middle and high latitudes throughout the year for both hemispheres. Waves of higher wavenumbers are rather weak in the summer hemisphere.Power spectral analysis of monthly r.m.s. wave amplitude for 24 months shows that the 12‐month period oscillation is prominent in middle and higher latitudes, while a 6‐month periodicity is observed in tropical latitudes for wavenumber one. The phase of maximum of the 6‐month cycle is about one month after the equinoxes, suggesting that planetary wave activity in lower latitudes is closely related to the semiannual oscillation of the equatorial zonal current in the upper stratosphere.Further analyses are made of seasonal characteristics of ‘transient’ waves to find the relationship between the wave motion and the mean zonal wind velocity. The predominant period (or phase velocity) is determined by a power spectral analysis using the Doppler effect due to the east‐west motion of waves. With wavenumber one in the upper stratosphere, a 15‐ to 20‐day period standing oscillation is observed in wintertime, while a 10‐day period westward moving wave is found in the summer hemisphere. During the spring and autumn, a standing oscillation with a period of about 3 weeks can be seen together with an 8‐ to 10‐day period westward motion. Higher wavenumbers show eastward motion in winter and no significant periodicity is found in other seasons as the wave activity is weak.These characteristic features of transient waves are explained by the theory of critical line absorption for vertical wave propagatio

ISSN:0035-9009    

DOI:10.1002/qj.49710243405

出版商:John Wiley&Sons, Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractThe difference between the true sea‐surface temperature and that inferred from satellite measurements of infrared radiances when viewing vertically through a cloud‐free atmosphere may be estimated to a useful accuracy for the 8–13μm radiometers of Defense Meteorological Satellite Program satellites. A simple parametric formula is developed that gives the difference to within ±0.6 K of that computed by a numerical method of solving the equation of radiative transfer. A comparison with data suggests that accuracies ⩽1.3K may be achieved relative to the actual value. Further work is necessary to confirm this accuracy because of an apparent discrepancy in the satel

ISSN:0035-9009    

DOI:10.1002/qj.49710243406

出版商:John Wiley&Sons, Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractFlux‐angle distributions of momentum derived from measurements of a UVW propeller anemometer were compared with results from a three‐component sonic anemometer and were found similar. Under unstable and near neutral conditions, momentum fluxes were negative both at small angles of attack for updraughts and at large angles of attack for downdraughts. At other angles of attack, the momentum flux‐angle distribution was always positive. A flux‐angle distribution algorithm is presented which shows the relative contribution made by each angle of attack of the flow to the tot

ISSN:0035-9009    

DOI:10.1002/qj.49710243407

出版商:John Wiley&Sons, Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractA method for deriving cloud top heights using satellite remote temperature sounding instruments is described. The weighting functions of a 15μm CO2tropospheric temperature sounder are modified by the presence of cloud in the sounding column. The relative effect of cloud on two or more such weighting functions in successive soundings along an orbital or scanning track is shown to be a simple function of cloud height. The method permits cloud heights to be found without the need to derive cloud amount. Results from the Nimbus 5 Selective Chopper Radiometer are presented

ISSN:0035-9009    

DOI:10.1002/qj.49710243408

出版商:John Wiley&Sons, Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractThis paper describes a series of numerical experiments designed to explore the close interplay between the rotational, the pressure gradient, and the buoyancy, force fields in concentrated vortex flows driven thermally by heating from below. The calculations are motivated by a desire to understand the dynamics of dust‐devils and to provide a theoretical framework in terms of which both past and future observations of these vortices may be interpreted.In the model, a vortex is generated along the vertical axis of a cylindrical region of fluid bounded by a rigid (no‐slip) lower boundary, and a sidewall consisting of a rigid, impermeable upper portion and a rotating, porous, lower portion through which fluid at ambient temperature enters the cylinder and acquires rotation. The flow is driven by maintaining a circular portion of the lower boundary at a fixed temperature above ambient and fluid is allowed to enter or leave the cylinder normally through the upper boundary. For a cylinder of given size, the flow behaviour depends on the magnitudes of two nondimensional parameters which characterize the strength of the thermal forcing and of the imposed rotation. According to the sizes of these, flows with axial downflow on part or all of the axis of rotation are possible and, in some cases, a closed cell of reversed flow is possible. In each case it is possible to give a complete description of the force field balance which combines to produce the particular flow pattern.The calculations go a long way to providing an understanding of the main features of dust‐devils as observed in a careful and detailed study by Sinclair and corroborate well with the experimental results of Fitzgarrald in relation to laboratory vortices. In particular, we show how rotationally induced axial pressure gradients can supplement buoyancy forces in accelerating the vertical flow in dust‐devils as appears necessary to explain the large vertical accelerations observed near the ground in these v

ISSN:0035-9009    

DOI:10.1002/qj.49710243409

出版商:John Wiley&Sons, Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractDuring the northern summer of 1975, 45 superpressure constant‐level balloons were released from the Seychelles Islands (4.7°S 55.5°E) for flight at 955mb (500m), 910mb (1000m) and 860mb (1500m) within the tropical boundary layer. The balloons were located by the Random Access Measurement System (RAMS) of the Nimbus‐6 satellite. This spacecraft also operated as a data relay system and collected pressure measurements performed by transducers carried by the balloons. The mean lifetime of the balloons was about 4–5 days, some of them lasting more than 8 days. Low‐level Lagrangian air trajectories in the southwesterly flow over the Arabian Sea are presented. They show the drastic changes in the airflow direction over the southwestern Arabian Sea associated with high or low activity periods of the monsoon over the western coast of India. During the first period of the experiment, the airflow over the southwestern Arabian Sea joins the low‐level jet flowing to the east of the Somali coast. This change, due to intense convective activity near Somalia, can be associated with a break in the monsoon activity. During the second period the air joins the Bay of Bengal branch of the monsoon over the southwest coast of India. Before the end of July a complete reversal of the winds over the Seychelles Islands is observed and some balloons drift towards Madagascar. During the third period the air flow over the Arabian Sea resumes a southwesterly direction and at the beginning of August it seems to join again the Bay of Bengal branch of the monsoon.Thus this experiment shows that low‐level ballooning can be used to map air currents over vast unsurveyed areas

ISSN:0035-9009    

DOI:10.1002/qj.49710243410

出版商:John Wiley&Sons, Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractDiffusion measurements in a modelled mixed layer support the equivalence of an instantaneous line‐source concentration field without a mean wind and a continuous point source with a mean wind when use is made of Taylor's translation hypothesis. Taylor's hypothesis as applied to mixed‐layer diffusion appears to break down in this type of flow for values ofs̀u/U>0.5, wheres̀uis the horizontal turbulence velocity component andUis the uniform mean wind. Variations in expected levels of cross‐wind integrated concentration are presented as a function of height and distance downstream from the source for a sampling duration of 4zi/U, whereziis the mixed‐la

ISSN:0035-9009    

DOI:10.1002/qj.49710243411

出版商:John Wiley&Sons, Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractRepresentative annual rainfall totals, expressed as percentages of appropriate standards, are given for most of the years from 1725 to the present for each of 11 regions covering most of England. The evidence for these values is discussed, and their relationships examined as groundwork for the production of long series of monthly rainfall totals for regions covering almost the whole of Great Britain.

ISSN:0035-9009    

DOI:10.1002/qj.49710243412

出版商:John Wiley&Sons, Ltd    

年代:1976

数据来源: WILEY